Indicated Airspeed (IAS) of an aircraft is determined by an airspeed system of the aircraft and is typically an input into flight performance management systems. Analysis of fuel mileage data has indicated that many aircraft are actually flying slightly faster than the (IAS) due to normal variations of typical production airspeed systems.
When an aircraft is flying faster than optimum cruise IAS, the rapid increase in airframe drag must be overcome by additional engine thrust and hence higher fuel burn. A small negative bias in IAS will cause the autopilot to fly the aircraft slightly faster than expected. The resulting fuel mileage calculation will indicate an excessive deviation due to a real effect of burning excess fuel to overcome excess drag and a false perception caused by comparing to production rated fuel mileage at slower than actual airspeed. The false perception of high fuel burn may be a significant economic factor because actual—vs—predicted fuel burn is routinely used as a feedback mechanism to adjust mission fuel predictions for individual aircraft. If such an airplane were gross weight limited on a particular route then revenue payload must be reduced to offset the weight of excess fuel.
For example, a cruise speed bias of only two or three miles per hour on a large commercial aircraft may inadvertently waste more than one hundred thousand gallons of fuel per year. Since both real and perceived effects are similar in size, the resulting increase in airplane takeoff weight due to the bias in mission planning could be double the amount needed to offset excess fuel bum during cruise. Over the course of a year the accumulation of unrealized airplane performance could exceed more than one million pounds per airplane. The combined impact of higher fuel expenses and potentially lower payload revenue could be considerable for operators with a large fleet of airplanes
Previous attempts to solve this recurring problem have focused on eliminating airspeed biases by performing a one-time change to airspeed calibration for an entire fleet of aircraft. However, these attempts do not take into consideration variations that occur from one aircraft to the next.
Therefore, there is an unmet need in the art for an ability to precisely adjust each aircraft's airspeed system in order to provide more accurate cruise IAS, thereby providing more optimum fuel efficiency.